1. Field of the Invention
The present invention relates to a noise absorption mounting structure for a working vehicle such as a hydraulic excavator and, more particularly, to a structure for mounting the noise absorption blades which can be tuned optimum against noises.
2. Related Art
In order to introduce the air for cooling the radiator or oil cooler of a working vehicle, an air hole is formed in the cover of an engine room or the like. Noise absorption blades may be mounted in the air hole so as to make lower the noises. This noise absorption blade mounting structure of the prior art is disclosed in Unexamined Published Japanese Patent Application No. H9-123771, for example, of which FIG. 20 is a section of an air hole portion.
In FIG. 20, a cooling wind intake duct 56 is disposed in the space between an opening 52 in the upper portion of an engine room 51 and the front face portions of a radiator 53 and an oil cooler 54. The cooling wind intake duct 56 is composed of a plurality of wind guide plates 57a to 57f, by which a cooling wind 58 taken from the opening 52 is divided and is homogeneously introduced to the radiator 53 and the oil cooler 54. On the other hand, the wind guide plates 57a to 57f are covered on their faces exposed to the wind with noise absorption members 59a to 59j, and the exit end portions of the individual wind guide plates 57a to 57f are sufficiently spaced from the front face portions of the radiator 53 and the oil cooler 54. Thus, the noises emanating out of the engine room 51 are lowered, and the flow velocity fluctuation of the cooling wind 58 in the cooling wind intake duct 56 is suppressed to reduce the noises of a cooling fan 55.
Another technique of the prior art is disclosed in Unexamined Published Japanese Utility Model Application No. H5-50027, for example. FIGS. 21 and 22 are a front elevation and a sectional view of an air hole portion, as disclosed. FIG. 22 is a sectional view taken along line Fxe2x80x94F of FIG. 21.
In FIGS. 21 and 22, noise absorption blades 61 are so mounted in the inner side portion 63 of a front mask 62 as to confront the whole area or a radiator core 64. When the front mask 62 is demounted for cleaning the radiator core 64, the noise absorption blades 61 can be demounted together with the front mask 62. Moreover, this front mask 62 mounting the noise absorption blades 61 are so hinged to a radiator guard 66 through a hinge mechanism 65 as can be opened and closed, and are fixed on the radiator guard 66 by means of bolts 67. This construction makes it easy to assemble the noise absorption blades 61 and to clean the radiator core 64.
However, the prior arts thus far described have the following problems.
In the former technique disclosed in Unexamined Published Japanese Patent Application No. H9-123771, the wind guide plates 57a to 57f are fixed in the engine room 51. This raises problems that no tuning can be made against the noises and that the noise absorption members 59a to 59j cannot be replaced even when they are deteriorated. On the other hand, the wind guide plates 57a to 57f and the noise absorption members 59a to 59j have different shapes and are high at their manufacture costs.
In the latter technique disclosed in Unexamined Published Japanese Utility Model Application No. 5-50027, on the other hand, There is caused by the structure of the noise absorption blades 61 a problem that the tuning is made difficult against the noises. Therefore, it takes a long time to design the noise reduction. Although a number of ventilation holes 62a are formed in the front mask 62, however, they have such a high ventilation resistance as to raise problems that the wind noises are high and that an air flow cannot be increased.
Noting the above-specified problems of the prior art, the invention has an object to provide a noise absorption blade mounting structure for a working vehicle, which is enabled to be excellent in the draft straightening property in an air hole of the cover of an engine room and excellent in the strength and appearance of the cover, by making noise absorption blades having a high noise absorption effect of a simple structure to mount/demount the noise absorption blades simply in/from the air hole thereby to facilitate the tuning against the noises coming from the engine room and the maintenances of the noise absorption blades.
In order to achieve the aforementioned object, according to a first aspect of the invention, there is provided a noise absorption blade mounting structure for a working vehicle, comprising: a cover covering a noise source including an engine, a cooling fan and a hydraulic unit and having an air hole for ventilating the ambient air therethrough, the cover being capable of being opened and closed; and a plurality of noise absorption blades disposed in the vicinity of the air hole for absorbing the noises which might otherwise leak from the inside to the outside of the cover. Each of the noise absorption blades includes: a core member; noise absorption members mounted on the two faces of the core member; and mounting members formed on the end faces of the noise absorption members. The cover includes in its air hole straightening members for straightening the draft in front of, as taken in the ventilation direction, the noise absorption blades.
According to the first aspect of the invention, the noise absorption members are mounted on the two faces of the core member so that the noise absorption is effected on the two faces of the ventilation passage. Therefore, the noise absorption area is doubled even with the noise absorption member having the same thickness as that of the prior art so that the noise absorption effect is improved. Since the core member is sandwiched between the noise absorption members, moreover, there is effected a damping act on to attenuate the sound waves, when reflected on the core member, by their energy loss. On the other hand, the sound waves, as emanating from the opposite side of the core member, are also attenuated by the noise absorption action of the noise absorption member on the opposite side of the core member so that the noise absorption effect is further improved.
As a result, even with the simple construction and the same size as that of the prior art, the noise absorption blades can be given a high noise absorption reducing effect at the air hole of the vehicle.
On the other hand, the mounting members are formed at the end faces of the noise absorption member so that the noise absorption blades can be firmly mounted on the vehicle body by the simple construction having a small number of parts.
As a result, the noise absorption blades are given a structure capable of enduring the severe vibrations or impacts on the vehicle.
Since the noise absorption blades have the simple construction, moreover, their individual components are set as the standard parts. By cutting and bending works simply, therefore, the noise absorption blades of special sizes can be easily manufactured in relation to the noise sources or the peripheral devices so that they can be easily tuned at low costs.
On the other hand, he straightening members for straightening the draft are disposed in front of the noise absorption blades and in the air hole of the cover so that the draft flows smoothly with little ventilation resistance but without any vortex or separation. As a result, there can be retained, a sufficient cooling wind. On the other hand, the dust or moisture is prevented from coming from the end faces of the noise absorption members at the end portions, as taken in the ventilation direction, of the noise absorption blades so that the noise absorption effect can be prevented from aging.
Moreover, the straightening member also acts as a strengthening member to retain the strength of the air hole of the cover, and the noise absorption blades and their mounting portions are located at the back of the straightening members thereby to provide a satisfactory appearance.
According to a second aspect of the invention, there is provided a noise absorption blade mounting structure for a working vehicle, comprising: a cover covering a noise source including an engine, a cooling fan and a hydraulic unit and having an air hole for ventilating the ambient air therethrough, the cover being capable of being opened and closed; and a plurality of noise absorption blades disposed in the vicinity of the air hole for absorbing the noises which might otherwise leak from the inside to the outside of the cover. Each of the noise absorption blades includes: a core member; noise absorption members on the two faces of the core member; and mounting members formed on the end fades of the noise absorption members. The mounting members are detachably mounted at their one-side end portions on the frames of the air hole of the cover.
According to the second aspect of the invention, the noise absorption members are mounted on the two faces of the core member so that the noise absorption is effected on the two faces of the ventilation passage. Therefore, the noise absorption area is doubled even with the noise absorption member having the same thickness as that of the prior art so that the noise absorption effect is improved. Since the core member is sandwiched between he noise absorption members, moreover, there is effected a damping action to attenuate the sound waves, when reflected on the core member, by their energy loss. On the other hand, the sound waves, as emanating from the opposite side of the core member, are also attenuated by the noise absorption action of the noise absorption member on the opposite side of the core member so that the noise absorption effect is further improved.
As a result, even with the simple construction and the same size as that of the prior art, the noise absorption blades can be given a high noise absorption reducing effect at the air hole of the vehicle.
On the other hand, the mounting members are formed at the end faces of the noise absorption member so that the noise absorption blades can be firmly mounted on the vehicle body by the simple construction having a small number of parts.
As a result, the noise absorption blades are given a structure capable of enduring the severe vibrations or impacts on the vehicle.
Since the noise absorption blades have the simple construction, moreover, their individual components are set as the standard parts. By cutting and bending works simply, therefore, the noise absorption blades of special sizes can be easily manufactured in relations the noise sources or the peripheral devices so that they can be easily tuned at low costs.
On the other hand, the one-side end portions of the mounting members are mounted on the air hole frames so that no mounting bracket for the noise absorption blades need be additionally provided to reduce the weight.
The noise absorption blades are detachably mounted so that they can be easily replaced or cleaned for maintenances by opening the cover. On the other hand, the noise absorption blades move together with the cover so that the radiator or the oil cooler can be easily cleaned by opening the cover.
In the second aspect of the invention, according to a third aspect, the mounting members include, at their one-side end portions, mounting portions perpendicular to the ventilation direction for fastening the noise absorption blades in parallel with the ventilation direction.
According to the third aspect, the mounting portions, as perpendicular to the ventilation direction, are disposed at the one-side end portions of the mounting members, and the noise absorption blade is fastened in parallel with the ventilation direction, so that the core member does not become loose. As a result, the noise absorption blades can be easily stacked without deteriorating the straightening effect. On the other hand, the noise absorption blade is not distorted to eliminate the problem that the appearance is poor.
In the first and second aspects of the invention, according to a fourth aspect, noise absorption blades having a larger noise absorption area are arranged an the front projection of at least the cooing fan.
According to the fourth aspect, in the front projection of at least the cooling fan, there are arranged the noise absorption blades which have a larger noise absorption area, so that the serious noises in the vicinity of the cooling fan having much flow rate and many rotary portions can be easily reduced and tuned to a low level by the inexpensive method.
In the first and second aspects of the invention, according to a fifth aspect, joint members joint the mounting members of the noise absorption blades to each other.
According to the fifth aspect, the mounting members of the noise absorption blades are jointed to each other by the joint member, the noise absorption blades are integrated to have a mounting structure of a box structure. As a result, the rigidity is improved together to apply no excessive force to the mounting portions of the noise absorption blades this construction is effective especially for the-noise absorption blades of a cantilever mounting structure having a large noise absorption area.